JP2021509441A - Bidirectional electromagnetic steel sheet and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bidirectional electromagnetic steel sheet having excellent magnetism in a rolling direction and a rolling vertical direction, and a method for manufacturing the same. SOLUTION: In% by weight, Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0.003%, Mn: 0.02 to 1.0. %, N: 0.003% or less (excluding 0%), C: 0.01% or less (excluding 0%), Ti: 0.01% or less (excluding 0%), P: 0.005 It contains ~ 0.10%, the balance contains Fe and other unavoidable impurities, and is characterized by satisfying the following equation (1). [Equation 1] [Mn] / [S] ≧ 60 (In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S, respectively.) [Selection diagram] No figure.

Description

Regarding the bidirectional magnetic steel sheet and its manufacturing method, more specifically, the bidirectional magnetic steel sheet having excellent magnetism in the rolling direction and the rolling vertical direction by appropriately controlling the ratio of Mn and S in the alloy composition. And its manufacturing method.

In order to improve the magnetic flux density of electrical steel sheets, it is known that the most effective method is to improve the texture of steel and align the <100> axes in parallel in the magnetization direction. A method is used in which the magnetic flux density is improved by reducing the amount of alloy and increasing the proportion of Fe atoms in the steel to bring the saturation magnetic flux closer to that of pure iron. Of these, in the case of grain-oriented electrical steel sheets, the {110} <001> orientation called the Goss orientation is used, and usually slab-hot-rolled-hot-rolled plate annealing-cold-rolled-decarburization during primary recrystallization- It can be obtained through a nitriding-second high temperature annealing process. However, this is excellent in magnetism only in the rolling direction (Rd direction), and the magnetism is extremely inferior in the rolling vertical direction (TD direction), making it difficult to use except for transformers whose magnetization direction is determined in the rolling direction. is there. Therefore, it is required to manufacture an electromagnetic steel sheet having a texture different from this and in which the texture in which the magnetization direction and the <100> axis are parallel is controlled.

Since the magnetization direction in a rotating device usually rotates in the plate surface, the <100> axis must be parallel to the plate surface, but the orientation often observed in steel materials in the orientation under such conditions. Is the {100} <011> orientation. This is because the <100> axis is parallel to the direction distorted in the vertical direction (TD direction) of 45 degrees rolling from the rolling direction, so the most excellent magnetic feature when the magnetization direction is 45 degrees from the rolling direction of the plate. There is. However, this orientation is a stable cold rolling orientation, and has the characteristic of disappearing during recrystallization annealing, and is not used in electrical steel sheet materials.

Similar to this, there is a {100} <001> orientation, which has been recognized as useful in the past as a Cube on face orientation, but it is actually a large scale such as cross-rolling or vacuum annealing. Only methods are known for manufacturing through equipment that cannot be industrially produced.

In particular, the cross-rolling method cannot be used because continuous production of materials is not possible, but in the case of large-scale power generation equipment, it is necessary to manufacture a cylindrical core with a diameter of several meters, so the core is made on the plate surface. It cannot be applied to the process of dividing into several to several tens of pieces and assembling them, and the productivity becomes extremely low.

In the case of a generator, a general turbine generator produces electricity in accordance with the commercial electric frequency of each country, 50 Hz or 60 Hz, so magnetic properties at 50 Hz and 60 Hz are important, but wind power generators, etc. Such magnetic properties under DC and 30 Hz are important for slow rotating generators.

Therefore, in the above-mentioned equipment, the magnetic flux density characteristic indicating the degree of magnetization is more important than the iron loss generated by AC magnetism, but this is generally evaluated by the B8 magnetic flux density. B8 magnetic flux density means the magnetic flux density value of a steel plate when the magnetic field strength is 800 A / m, which is mainly measured by AC magnetism of 50 Hz, and in some cases, measured by direct current or at a frequency of 50 Hz or less. I also measure it.

Provided are a bidirectional electromagnetic steel sheet and a method for manufacturing the same. Specifically, a bidirectional electromagnetic steel sheet having excellent magnetism in the rolling direction and the rolling vertical direction and a method for producing the same are provided by appropriately controlling the ratio of Mn and S in the alloy composition.

The grain-oriented electrical steel sheet according to one embodiment of the present invention is Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0.003% in weight%. , Mn: 0.02 to 1.0%, N: 0.003% or less (excluding 0%), C: 0.01% or less (excluding 0%), Ti: 0.01% or less (0%) , P: 0.005 to 0.10%, the balance is composed of Fe and other unavoidable impurities, and satisfies the following equation 1.
[Number 1]
[Mn] / [S] ≧ 60
(In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S, respectively.)

One or more of Sb: 0.001 to 0.1% by weight and Sn: 0.001 to 0.1% by weight can be further contained.
Mo: 0.01% by weight or less, Bi: 0.01% by weight or less, Pb: 0.01% by weight or less, Mg: 0.01% by weight or less, As: 0.01% by weight or less, Be: 0.01 One or more of Sr: 0.01% by weight or less can be further contained.

The surface integral of the crystal grains having an orientation within 15 ° from {100} <001> may be 60 to 99%.

A forsterite layer is formed on the electromagnetic steel sheet, and the forsterite layer may have a fraction of an area having a thickness of 2 μm or less from the surface of the electromagnetic steel sheet of 75% or more.

An insulating layer is formed on the forsterite layer, and the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer are 0.2 to 8 μm, respectively, and the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer. The difference may be 50% or less of the thickness of the lower surface insulating layer.

The average roughness (Ra) of the upper surface insulating layer and the average roughness (Ra) of the lower surface insulating layer are 1 μm or less, respectively, and the average roughness (Ra) of the upper surface insulating layer and the average roughness of the lower surface insulating layer (Ra). The difference in Ra) may be 0.3 μm or less.

Br in the rolling direction and the rolling vertical direction are all 1.65T or more, Br in the circumferential direction is 1.55T or more, and Br is calculated by the following equation 2.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. )

When a magnetic field of 1.5 T is applied, the magnetic permeability UDC at a measurement frequency of 0.01 Hz or less may be 1.2 times or more the magnetic permeability U50 at 50 Hz.

The Br value measured after annealing the electromagnetic steel sheet at a temperature of 750 ° C. to 880 ° C. for 1 to 2 hours may be 1.65 T or more. Br is calculated by the following equation 2.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. )

Bh in the rolling direction is 1.8T or more, Bh in the vertical rolling direction is 1.7T or more, Bh in the circumferential direction is 1.6T or more, and Bh is calculated by the following equation 3.
[Number 3]
Bh = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B25
(In Equation 3, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B25 indicates the strength of the magnetic field (Tesla) induced when induced at 2500 A / m. )

The method for producing a bidirectional electromagnetic steel sheet according to an embodiment of the present invention is, in% weight, Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0. .003%, Mn: 0.02 to 1.0%, N: 0.001 to 0.01%, C: 0.02 to 0.06%, Ti: 0.01% or less (not including 0%) ), P: 0.005 to 0.10%, the balance is composed of Fe and other unavoidable impurities, the stage of producing a slab satisfying the following number 1, the stage of heating the slab, and the stage of hot rolling the slab. The stage of manufacturing the hot-rolled plate, the stage of cold-rolling the hot-rolled plate to manufacture the cold-rolled plate, the stage of primary recrystallization annealing of the cold-rolled plate, and the stage of primary recrystallization annealing of the cold-rolled plate are secondary. Including the step of recrystallization annealing.
[Number 1]
[Mn] / [S] ≧ 60
(In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S, respectively.)
The slab can satisfy the following number 4.
[Number 4]
[C] / [Si] ≧ 0.0067
(In Equation 4, [C] and [Si] indicate the contents (% by weight) of C and Si in the slab, respectively.)

At the stage of heating the slab, the time of 1100 ° C. or higher may be 25 to 50 minutes.

At the stage of manufacturing the hot-rolled plate, two or more passes are included, the reduction rate in the final pass and the pass before the final pass is 15 to 40%, respectively, and in the final pass and the pass before the final pass. The total reduction rate may be 55% or less.

After the step of manufacturing the hot-rolled plate, the step of annealing the hot-rolled plate is further included, and the time of 1100 ° C. or higher may be 5 to 50 seconds at the stage of annealing the hot-rolled plate.

After the step of annealing the hot-rolled plate, the average crystal grain size of the hot-rolled plate may be 100 to 200 μm.

After the step of annealing the hot-rolled plate, the number of precipitates having a particle size of 0.1 μm or more in a 1 mm2 area of the hot-rolled plate is 100 to 4000, and the number of precipitates exceeding the particle size of 0.5 μm. The ratio (A / B) of the number of precipitates (A) having a particle size of 0.1 to 0.5 μm to (B) may be 1 or more.

The temperature at the stage of annealing the hot-rolled plate (T2) and the temperature at the stage of heating the slab (T1) can satisfy the following equation (5).
[Number 5]
-200 ≤ T1-T2 ≤ 30

The time from the step of heating the slab to the step of manufacturing the hot-rolled plate is 3 to 20 minutes, and the maximum temperature from the step of heating the slab to the stage of manufacturing the hot-rolled plate is the hot-rolling. The annealing temperature at the stage of plate annealing may be 20 ° C. or lower.

At the stage of manufacturing the cold-rolled plate, the reduction rate may be 50 to 70%.
At the stage of primary recrystallization annealing, the amount of nitriding may be 0.01 to 0.023% by weight.

After the step of primary recrystallization annealing, the average crystal grain size of the primary recrystallization annealed steel sheet may be 32 to 50 μm.

After the step of primary recrystallization annealing, a step of applying an annealing separator containing MgO can be further included.

The bidirectional electromagnetic steel sheet according to the embodiment of the present invention has excellent magnetism in the rolling direction and the rolling vertical direction by appropriately controlling the ratio of Mn and S in the alloy composition.
In particular, it can be usefully used for a generator having a slow rotation speed such as a wind power generator.

Terms such as first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, area, layer or section from another part, component, area, layer or section. Therefore, the first part, component, region, layer or section described below may be referred to as the second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is merely to refer to a particular embodiment and is not intended to limit the invention. The singular form used herein also includes multiple forms unless the wording has a clear opposite meaning. As used herein, the meaning of "contains" embodies a particular property, region, integer, stage, behavior, element and / or component, and other characteristics, region, integer, stage, behavior, element and / or. It does not exclude the presence or addition of ingredients.

When referring to one part being "above" another part, it may be directly above or above the other part, or may be intervened by another part in between. In contrast, when one mentions that one part is "directly above" another, no other part is intervened between them.

Although not specifically defined, all terms, including the technical and scientific terms used herein, have the same meaning as generally understood by those with ordinary knowledge in the technical field to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted to have meanings that are consistent with the relevant technical literature and what is currently disclosed, and unless defined, they are not interpreted in an ideal or very formal sense.

Further, unless otherwise specified,% means% by weight, and 1 ppm is 0.0001% by weight.

In one embodiment of the present invention, the meaning of further containing an additional element means that iron (Fe), which is the balance, is contained in place of the additional amount of the additional element.

Hereinafter, examples of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention belongs can easily carry out the examples. However, the present invention can be realized in a variety of different forms and is not limited to the examples described herein.

The grain-oriented electrical steel sheet according to one embodiment of the present invention is Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0.003% in weight%. , Mn: 0.02 to 1.0%, N: 0.003% or less (excluding 0%), C: 0.01% or less (excluding 0%), Ti: 0.01% or less (0%) Includes), P: 0.005 to 0.10%.

First, the reason for limiting the components of the bidirectional electromagnetic steel sheet will be described.
Si: 2.0 to 6.0% by weight
Silicon (Si) is an element that forms austenite in hot rolling, and it is necessary to limit the amount of silicon (Si) added in order to have an austenite fraction inside and outside 10% near the slab heating temperature and near the hot-rolled sheet annealing temperature. There is. Further, in the secondary recrystallization annealing, the formation of the secondary recrystallization fine structure can occur smoothly at the time of annealing only in the case of the ferrite single phase, so it is necessary to limit the components to the ferrite single phase. In pure iron, a ferrite single phase is formed when 2.0% by weight or more is added, and the austenite fraction can be adjusted through the addition of C. Therefore, the lower limit of the Si content should be limited to 2.0% by weight. Can be done. Further, when 6% by weight is exceeded, cold rolling is impossible, so this is limited. More specifically, Si may be contained in an amount of 2.2 to 3.1% by weight. More specifically, in order to obtain a steel sheet having a high magnetic flux density, Si may be contained in an amount of 2.4 to 2.9% by weight.

Al: 0.0005 to 0.04% by weight
Aluminum (Al) forms AlN and is used as an inhibitor for secondary recrystallization. In one embodiment of the present invention, since the Cube texture can be obtained even when an inhibitor is used other than the nitriding step of the ordinary grain-oriented electrical steel sheet, the amount of Al added is controlled in a wider range than that of the grain-oriented electrical steel sheet. May be good. However, when less than 0.0005% by weight is added, the oxide in the steel increases significantly to make the magnetism inferior, and the secondary recrystallization temperature is changed to hinder the formation of the Cube orientation. It shall be 0.0005% by weight. If it exceeds 0.04% by weight, the secondary recrystallization temperature will increase significantly, making industrial production difficult. More specifically, Al may be contained in an amount of 0.001 to 0.003% by weight.

S: 0.0001 to 0.003% by weight
Sulfur (S) combines with Cu and Mn in steel to form MnS finely, and the finely formed precipitates assist secondary recrystallization, so the amount added is 0.0001 to 0.003 by weight. Can be%. When added in an excessive amount, the segregation of S does not control the surface defects and the texture at the time of secondary recrystallization, so the content is limited to 0.003% by weight.

Mn: 0.02 to 1.0% by weight
Manganese (Mn) is inevitably present in molten steel, but if it is contained in a small amount, it can be used as a precipitate, and it can be added to steel as an element that changes to MnS after the formation of FeS. However, if it exceeds 1.0%, surface defects due to Mn during high-temperature annealing become a problem, so the limit is set to 1.0%. If it is contained less than 0.02% by weight, the magnetism becomes inferior, so the lower limit is set to 0.02% by weight. More specifically, Mn may be contained in an amount of 0.05 to 0.5% by weight.

Mn / S weight ratio: 60 or more Mn / S is a numerical value used to prevent hot-rolled brittleness during hot rolling, and it is known that 10 to 20 is suitable for grain-oriented electrical steel sheets. In the present invention, it is necessary to maintain a sufficiently high Mn / S weight ratio in order to suppress Goss growth due to S. By controlling the Mn / S weight ratio, the formation temperature, size, and distribution of the precipitate formed by the bond between Mn and S can be controlled, and the Mn / S weight ratio can be adjusted during secondary recrystallization. It is possible to strengthen the Cube texture and improve the magnetic flux density in the rolling direction and the rolling vertical direction. Therefore, the Mn / S weight ratio can be controlled to 60 or more. More specifically, the Mn / S weight ratio can be controlled to 130 to 1000.

N: 0.003% by weight or less Nitrogen (N) is an element that forms AlN, and since AlN is used as an inhibitor, it is necessary to secure an appropriate content. When N is contained in an excessively small amount, the degree of microstructure non-uniform deformation is sufficiently increased during cold rolling to promote the growth of Cube during primary recrystallization, and the growth of Goss cannot be suppressed. When N is contained in an excessive amount, not only surface defects such as blister due to nitrogen diffusion are induced in the post-rolling process, but also excess nitrate is formed in the slab state, which makes rolling difficult. , Causes the manufacturing unit price to rise. More specifically, N can contain 0.001 to 0.003% by weight.

N may be contained in the slab in an amount of 0.001 to 0.1% by weight. In one embodiment of the present invention, the process of nitriding is included during the primary recrystallization annealing, and a part of N is removed during the secondary recrystallization annealing, so that the N content of the slab and the final manufactured electrical steel sheet are different. You may.

C: 0.01% by weight or less If a large amount of carbon (C) is contained even after the secondary recrystallization annealing, magnetic aging occurs and iron loss greatly increases. Therefore, the upper limit is 0.01% by weight. More specifically, it is adjusted to 0.005% by weight or less. More specifically, C can be contained in an amount of 0.0001 to 0.005% by weight.

In the slab, C may be contained in an amount of 0.02 to 0.06% by weight. Through this, stress concentration and Goth formation in the hot-rolled plate can be suppressed, and the precipitate can be miniaturized. Further, C can increase the degree of microstructure non-uniform deformation during cold rolling, promote the growth of cubes during primary recrystallization, and suppress the growth of Goss. However, if it is added in an excessive amount, the stress concentration in the hot-rolled plate can be eliminated, but the formation of Goss cannot be suppressed, and it is difficult to miniaturize the precipitate. The amount of addition is limited in order to make the cold rollability significantly inferior even during cold rolling. Since one embodiment of the present invention includes a process of decarburization during primary recrystallization annealing, the C content of the slab and the final manufactured electrical steel sheet may be different.

Ti: 0.01% by weight or less,
Titanium (Ti) is preferably added in an amount of 0.01% by weight or less as an element for forming a composite precipitate such as TiSiCN or forming an oxide. Further, since the precipitates and oxides stable at high temperature interfere with the secondary recrystallization, it is necessary to add the amount to 0.01% by weight or less. However, it is extremely difficult to completely remove it in a normal steelmaking process. More specifically, Ti can be contained in an amount of 0.005% by weight or less.

P: 0.005 to 0.10% by weight
Phosphorus (P) plays a role of improving the specific resistance of steel, improving the fraction of Cube during secondary recrystallization, and also increases the amount of non-uniform deformation during cold rolling, so that it is at least 0.005% by weight or more. Is preferably added. However, since the cold rollability becomes extremely fragile when added in excess of 0.10% by weight, the amount of addition is limited. More specifically, P may be contained in an amount of 0.01 to 0.08% by weight.
One or more of Sb: 0.001 to 0.1% by weight and Sn: 0.001 to 0.1% by weight can be further contained.

Sn and Sb: 0.001% to 0.1%
Tin (Sn) and antimony (Sb) are elements that can be added for controlling the primary recrystallization texture. Further, if 0.001% by weight or more is added, it is an element that changes the formation thickness of the oxide layer and reduces the magnetic difference between the vertical rolling direction and the rolling direction. Limit this as it will greatly increase slippage in.

Mo: 0.01% by weight or less, Bi: 0.01% by weight or less, Pb: 0.01% by weight or less, Mg: 0.01% by weight or less, As: 0.01% by weight or less, Be: 0.01 One or more of Sr: 0.01% by weight or less can be further contained.

Molybdenum (Mo) has the effect of suppressing grain boundary embrittlement due to Si in electrical steel sheets when it is added as a segregating element to the grain boundaries, but on the other hand, it combines with C to form precipitates such as Mo carbides and becomes magnetic. Since it has an adverse effect, it is necessary to limit it to 0.01% by weight or less.

Bismuth (Bi), lead (Pb), magnesium (Mg), arsenic (As), beryllium (Be) and strontium (Sr) are elements in which oxides, nitrides and carbides are finely formed in steel. It is an element that helps the next recrystallization and can be added additionally. However, when it is added in excess of 0.01% by weight, it causes a problem that secondary recrystallization is unstable, so it is necessary to limit the amount of addition.

Further, in the bidirectional electromagnetic steel sheet of the present invention, the balance other than the above-mentioned components is Fe and unavoidable impurities. However, the content of other elements is not excluded as long as it does not interfere with the action and effect of the present invention.

As described above, the bidirectional electromagnetic steel sheet according to the embodiment of the present invention precisely controls the alloy composition to form a large number of cube textures. Specifically, the surface integral of the crystal grains having an orientation within 15 ° from {100} <001> may be 60 to 99%. At this time, if it exceeds 99%, it means that the formation of Island grains inevitably formed during the secondary recrystallization is suppressed and the precipitate is completely removed. This is limited to 60-99% as the annealing time in.

In one embodiment of the present invention, a forsterite layer is formed on the steel sheet, and the forsterite layer may have a fraction of an area having a thickness of 2 μm or less from the surface of the steel sheet of 75% or more. In grain-oriented electrical steel sheets, an oxide layer containing forsterite (Mg2SiO4) is formed to a thickness of 2 to 3 μm from the surface in order to apply tension in the rolling direction, and the tension is utilized by utilizing the difference in thermal expansion coefficient between this and the base metal. Is given. However, in the case of one embodiment of the present invention, the tension in the rolling direction immediately means compression in the rolling vertical direction, so it is preferable to extremely reduce this. Since the tension applying effect of a thin oxide layer of 2.0 μm or less is extremely reduced, the tension applied to the entire plate can be removed by distributing such a thin oxide layer in an area of 75 area% or more of the surface area.

An insulating layer is formed on the forsterite layer, and the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer are 0.2 to 8 μm, respectively, and the difference between the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer is as described above. It may be 50% or less of the thickness of the lower surface insulating layer. The forsterite layer may be formed on both surfaces (upper surface and lower surface) of the steel sheet, or an insulating layer may be formed on the forsterite layer formed on the upper surface and the lower surface thereof. The insulating layer formed on the upper surface is called an upper surface insulating layer, and the insulating layer formed on the lower surface is called a lower surface insulating layer. Appropriate insulation can be ensured by the insulating layers on the upper surface and the lower surface, and punching property for use in a generator or the like can be ensured. In particular, the difference in thickness between the upper surface insulating layer and the lower surface insulating layer can be controlled to suppress burs during punching.

The average roughness (Ra) of the upper surface insulating layer and the average roughness (Ra) of the lower surface insulating layer are 1 μm or less, respectively, and the average roughness (Ra) of the upper surface insulating layer and the average roughness (Ra) of the lower surface insulating layer are ) May be 0.3 μm or less. A material having a high roughness cannot suppress the bur at the time of punching, and particularly when the roughness difference between the upper surface and the lower surface is excessively large, the bur cannot be suppressed.

The bidirectional electromagnetic steel sheet according to the embodiment of the present invention is excellent in magnetism in the rolling direction and the rolling vertical direction. Specifically, Br in the rolling direction and the rolling vertical direction are all 1.65T or more, Br in the circumferential direction is 1.55T or more, and Br is calculated by the following equation 2.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. )

In the case of a large generator, the diameter of the annular frame is several meters, and the electromagnetic steel plate is cut by T-shaped teeth (Teeth) to form the annular frame. At this time, the T-shaped Yeth portion may be set in the rolling vertical direction and the rolling direction may be placed on the annular frame, or conversely, the T-shaped Teath portion may be placed in the rolling direction and the rolling vertical direction may be placed on the annular frame. it can. Such design changes are determined by the length of the teeth, the length of the diameter of the annular frame, and the width of the annular frame. Normally, the Teth portion is a portion through which a large magnetic flux flows when the generator is operating, and such magnetic flux escapes to the annular portion. In consideration of the energy generated at this time, it is decided whether the rolling direction and the rolling vertical direction are the Teth part or the annular part, but all Br are 1.65T or more and the magnetic flux density is very high. In the case of the material to have, since it is not necessary to distinguish which part the rolling direction and the rolling vertical direction are used for, in any case, the material has very high energy efficiency. Further, if the Br magnetic flux density in the circumferential direction becomes high at 1.55 T or more, the energy loss due to the magnetic flux at the T-shaped Teeth portion and the connecting portion of the annular frame is greatly reduced. Through this, it is possible to improve the efficiency of the generator or reduce the width of the annular frame and the size of the teeth portion to make a highly efficient generator even with a small-sized core.

By using an electromagnetic steel plate with a high Bh in the rolling direction of 1.8T or more and a very good characteristic in the rolling vertical direction of 1.7T or more, it was divided into electrical equipment with a high design magnetic flux, such as a generator or a motor. When machining in the form of a core or in a core that is used without splitting into smaller cores, the efficiency of the electrical equipment can be greatly improved by reducing the amount of exciting current through this.

When a magnetic field of 1.5 T is applied, the magnetic permeability UDC at a measurement frequency of 0.01 Hz or less may be 1.2 times or more the magnetic permeability U50 at 50 Hz.

Of the generators, in the case of a wind generator without gears, the rotating magnetic field is very slow, so the value of the current flowing through the circuit is greatly affected by the magnetic permeability of 0.01 Hz or less than the normal 50 Hz magnetic permeability. When the magnetic permeability of 0.01 Hz or less is 1.2 times or more higher than the magnetic permeability of 50 Hz, the heat generated by the current is greatly reduced and the efficiency of the generator can be improved.
The Br value measured after annealing the electromagnetic steel sheet at a temperature of 750 ° C. to 880 ° C. for 1 to 2 hours may be 1.65 T or more.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. )

Bh in the rolling direction is 1.8T or more, Bh in the vertical rolling direction is 1.7T or more, Bh in the circumferential direction is 1.6T or more, and Bh is calculated by the following equation 3.
[Number 3]
Bh = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B25
(In Equation 3, [Si] and [Al] indicate the contents (% by weight) of Si and Al, respectively. B25 indicates the strength of the magnetic field (Tesla) induced when induced at 2500 A / m. )

The method for producing a bidirectional electromagnetic steel sheet according to an embodiment of the present invention is, in% weight, Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0. .003%, Mn: 0.02 to 1.0%, N: 0.001 to 0.01%, C: 0.02 to 0.06%, Ti: 0.01% or less (not including 0%) ), P: 0.005 to 0.10%, the balance contains Fe and other unavoidable impurities, a step of producing a slab satisfying the following number 1, a step of heating the slab, and a step of hot rolling the slab. The stage of manufacturing the hot-rolled plate, the stage of cold-rolling the hot-rolled plate to manufacture the cold-rolled plate, the stage of primary recrystallization annealing of the cold-rolled plate, and the stage of primary recrystallization annealing of the cold-rolled plate 2 Includes the next step of recrystallization annealing.
[Number 1]
[Mn] / [S] ≧ 60
(In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S, respectively.)

Hereinafter, each step will be specifically described.
First, the slab is manufactured. Since the reason for limiting the addition ratio of each composition in the slab is the same as the reason for limiting the composition of the bidirectional magnetic steel sheet described above, a duplicate description will be omitted. The composition of slabs other than C and N does not substantially change during the manufacturing process such as hot rolling, hot-rolled sheet annealing, cold rolling, primary recrystallization annealing, and secondary recrystallization annealing, which will be described later. And the composition of the bidirectional electromagnetic steel sheet are substantially the same.
The slab can satisfy the following number 4.
[Number 4]
[C] / [Si] ≧ 0.0067
(In Equation 4, [C] and [Si] indicate the contents (% by weight) of C and Si in the slab, respectively.)

When C is contained in an excessively small amount or Si is contained in an excessive amount, it may be difficult to promote the growth of Cube and suppress the growth of Goss. More specifically, the left side of Equation 4 may be 0.0083 or more.
The slab can be manufactured by utilizing the thin slab method or the strip casting method. The thickness of the slab can be 200-300 mm.

Next, the slab is heated.
The time of 1100 ° C. or higher may be 25 to 50 minutes at the stage of heating the slab.
If the time of 1100 ° C. or higher cannot be properly secured, the crystal grain size of the hot-rolled plate cannot be properly secured, or a large amount of coarse precipitates of 0.5 μm or higher are generated, and the magnetism in the vertical rolling direction is appropriate. Cannot be secured.

Next, the slab is hot-rolled to produce a hot-rolled plate.
In the stage of manufacturing the hot-rolled plate, it contains two or more passes, the reduction rate in the final pass and the pass before the final pass is 15 to 40%, respectively, and the reduction rate in the final pass and the pass before the final pass. The total may be 55% or less.

The final pass of hot rolling has extremely poor rollability as the temperature at which the hot rolling temperature is the lowest. It is not preferable to roll at a large rolling reduction in such a temperature range. In addition, as the reduction rate increases in the last two passes, the fraction of crystal grains in the Goss direction tends to increase significantly on the surface of the hot-rolled plate. To suppress this, the reduction rate in each pass tends to increase. It is necessary to make it 10 to 40% or less, and make the total reduction rate in the two passes 55% or less.

The hot rolling end temperature can be 950 ° C. or lower. Since the hot rolling end temperature is low, the crystal grains having the stretched Cube orientation inside the hot-rolled plate accumulate more energy, which may increase the Cube fraction during hot-rolled plate annealing.
The thickness of the hot-rolled plate can be 1-2 mm.

After the step of manufacturing the hot-rolled plate, a step of annealing the hot-rolled plate can be further included.
The time of 1100 ° C. or higher may be 5 to 50 seconds at the stage of annealing the hot-rolled plate. This is to form fine precipitates after annealing on a hot-rolled plate, and it is necessary to limit the time in order to make the precipitates formed by the slabs finer without making them coarser.

Further, when the thickness of the slab is Tslab and the thickness of the hot-rolled plate is Hot-coil, the annealing time at 1100 ° C. or higher during the annealing time of the slab at the stage of heating the slab is the stage of annealing the hot-rolled plate. It can be carried out as short as 2 × Tslab / Hot-coil times or more and 4 × Tslab / Hot-coil times or less from the annealing time of the hot-rolled plate at 1100 ° C. or higher. This is to make the size of the precipitate formed by the slab finer, and since the slab is thicker than the hot-rolled plate, it is difficult to obtain fine precipitates more uniformly in the thickness direction. Therefore, it is possible to prevent the precipitate formed by the slab from being coarsened through the time limit.

After the step of annealing the hot-rolled plate, the average crystal grain size of the hot-rolled plate may be 100 to 200 μm. If the crystal grain size is coarsened, there is a high possibility that crystal grain nuclei in the Goss orientation will be formed by the shear band formed during rolling, so it is necessary to limit the size to 200 μm or less. is there. The crystal grain size can be measured by a method of measuring the diameter of a sphere assuming the same volume of spheres by a standard crystal grain size measuring method.

After the step of annealing the hot-rolled plate, the number of precipitates having a particle size of 0.1 μm or more in a 1 mm2 area of the hot-rolled plate is 100 to 4000, and the number of precipitates having a particle size exceeding 0.5 μm (B). The ratio (A / B) of the number of precipitates (A) having a particle size of 0.1 to 0.5 μm may be 1 or more.
This is because the Cube texture can be obtained only when the number of precipitates is appropriately secured. Further, only when the ratio of the coarse precipitate and the fine precipitate is appropriately formed, the secondary recrystallization can be smoothly performed, and the magnetism in the rolling direction and the rolling vertical direction can all be excellent.

The annealing temperature at the stage of annealing the hot-rolled plate may be 1000 to 1200 ° C.
The temperature at the stage of annealing the hot-rolled plate (T2) and the temperature at the stage of heating the slab (T1) can satisfy the following equation (5).
[Number 5]
-200 ≤ T1-T2 ≤ 30
If the number 5 is not satisfied, a large amount of coarse precipitates may be generated on the hot-rolled plate, and the magnetism in the vertical rolling direction may deteriorate.

The time from the stage of heating the slab to the stage of manufacturing the hot-rolled plate is 3 to 20 minutes, and the maximum temperature from the stage of heating the slab to the stage of manufacturing the hot-rolled plate is annealing at the stage of annealing the hot-rolled plate. The temperature may be 20 ° C. or lower.

The time from the stage of heating the slab to the stage of manufacturing the hot-rolled plate is properly maintained, and at the same time, the maximum temperature from the stage of heating the slab to the stage of manufacturing the hot-rolled plate is annealed at the stage of annealing the hot-rolled plate. By controlling the temperature relationship, the size of the precipitate can be made extremely fine and secondary recrystallization can be advantageous.

At the stage of manufacturing the cold-rolled plate, the reduction rate may be 50 to 70%. When the reduction rate is excessively high, there is a problem that a large number of GOSS crystals are formed. When the reduction rate is excessively low, there is a problem that the thickness of the final manufactured steel sheet becomes thick.

The amount of nitriding may be 0.01 to 0.023% by weight at the stage of primary recrystallization annealing. If the amount of nitriding is not properly secured, secondary recrystallization may not be smoothly formed, and a problem of deterioration of magnetism may occur.

After the step of primary recrystallization annealing, the average crystal grain size of the primary recrystallization annealed steel sheet may be 32 to 50 μm. If the average crystal grain size of the primary recrystallization annealed steel sheet cannot be appropriately secured, the secondary recrystallization may not be smoothly formed and a problem of deterioration of magnetism may occur.

After the step of primary recrystallization annealing, a step of applying an annealing separator containing MgO can be further included.
Since the forsterite layer formed by applying the annealing separator is the same as that described above, the overlapping description will be omitted.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited to the following examples.

Experimental Example 1
A slab consisting of the components shown in Tables 1 and 2 and the balance Fe and unavoidable impurities was produced, heated at 1150 ° C. and then hot-rolled to produce a 1.6 mm thick hot-rolled coil at 1100 ° C. to 1140 ° C. The hot-rolled annealed sheet, which was annealed at ° C. for 30 seconds, annealed at 900 ° C. for 90 seconds, and then rapidly cooled, was cold-rolled to a reduction ratio of 63%.

The cold-rolled plate was nitrided to 0.02 wt% and decarburized at a dew point of 60 ° C. and a hydrogen of 75% to a crystal grain size of 36 μm through a primary recrystallization annealing step. Then, after applying an annealing separator containing an MgO component, the temperature was raised to 1200 ° C. at a heating rate of 20 ° C. per hour, and then secondary recrystallization annealing was carried out over 20 hours. The cooled plate was subjected to an insulating coating after removing the MgO annealing separator, and the magnetism was measured and arranged in Table 3. Table 3 shows the results of re-measurement of magnetism after annealing at 800 ° C. for 2 hours after magnetism measurement.

As shown in Tables 1 to 3, it can be confirmed that the examples of the invention satisfying the alloy composition of the present invention have excellent magnetism. On the other hand, in the comparative example which does not satisfy the alloy composition of the present invention, it can be confirmed that the magnetism is poor.

Experimental Example 2
As shown in Table 4 below, the A1 specimen of Example 1 was formed with an upper surface insulating coating and a lower surface insulating coating without removing the annealing separator, and the magnetism was measured as shown below. It is organized in Table 5.

As shown in Tables 4 and 5, it can be confirmed that the invention examples satisfying the thickness fraction of the forsterite layer, the thickness of the upper surface and lower surface insulating layers, and the rough surface range are excellent in magnetism. On the other hand, in the comparative example which does not satisfy the thickness fraction of the forsterite layer, the thickness of the upper surface and lower surface insulating layers and the rough surface range, it can be confirmed that the magnetism in the rolling vertical direction is particularly deteriorated.

Experimental Example 3
By weight% Si: 2.8%, Al: 0.029%, S: 0.001%, Mn: 0.15%, N: 0.003%, C: 0.025%, Ti: 0.002 %, P: 0.05%, and a slab composed of the balance Fe and unavoidable impurities was produced. After heating the slab at 1150 ° C, it is hot-rolled to produce a hot-rolled coil with a thickness of 1.6 mm, annealed at 1100 ° C to 1140 ° C for 30 seconds, annealed at 900 ° C for 90 seconds, and then rapidly cooled. The plate was cold rolled at the rolling reduction rates listed in Table 6 below.

As shown in Table 6 below, the cold-rolled plate undergoes an annealing step of decarburizing or decarburizing in an atmosphere with a dew point of 60 ° C. and 75% hydrogen to obtain the average grain size shown in Table 6 below. I did. The non-nitriding primary recrystallization specimen was annealed at 1150 ° C. for 30 minutes at a temperature rise rate of 10 ° C./s in a 100% nitrogen atmosphere, and the nitrided specimen was annealed and separated mainly containing the MgO component. After the agent was applied, the temperature was raised to 1200 ° C. at a heating rate of 20 ° C. per hour, and then secondary recrystallization annealing was carried out over 20 hours. All the materials from the two annealing steps were coated with an insulating coating and the magnetism and cube fractions were measured.

As shown in Table 6, it can be confirmed that in the invention example satisfying the cold reduction ratio and the nitriding amount range, the cube structure is appropriately secured and the magnetism is excellent. On the other hand, if the cold reduction rate cannot be controlled appropriately or if nitriding is not performed, it can be confirmed that the magnetism in the vertical rolling direction deteriorates and the magnetism in the circumferential direction deteriorates.

Experimental Example 4
By weight% Si: 2.8%, Al: 0.029%, S: 0.001%, Mn: 0.15%, N: 0.003%, C: 0.025%, Ti: 0.002 %, P: 0.05%, and a slab composed of the balance Fe and unavoidable impurities was produced. The slab was heated at the temperatures shown in Table 7 below and then hot-rolled to produce a hot-rolled coil having a thickness of 1.6 mm. At this time, the hot rolling end temperatures are arranged in Table 7.

Then, it was annealed at the temperature shown in Table 7 below, and the average crystal grain size and precipitates of the annealed hot-rolled plate were arranged in Table 7 below. The number of precipitates was measured based on the precipitates having a diameter of 0.1 μm or more, and the number of precipitates within an arbitrary 1 m × 1 m area was measured.

Then, the hot-rolled annealed sheet was cold-rolled to a rolling reduction of 63%.
The cold-rolled plate was subjected to a primary recrystallization annealing step of nitriding to 0.02 wt% and decarburizing at a dew point of 60 ° C. and a hydrogen of 75% atmosphere so that the crystal grain size was as shown in Table 7 below. Then, after applying an annealing separator containing an MgO component, the temperature was raised to 1200 ° C. at a heating rate of 20 ° C. per hour, and then secondary recrystallization annealing was carried out over 20 hours. Insulation coating was applied, magnetism was measured, and Table 8 was arranged.

As disclosed in Tables 7 to 8, D1 to D4, D6, and D7, for which the primary recrystallization diameter could not be appropriately secured, have deteriorated magnetism in the vertical rolling direction and poor magnetism in the circumferential direction. Can be confirmed.

In particular, it can be confirmed that the heating temperature of D4 is much higher than the annealing temperature of the hot-rolled plate, the grain size of the hot-rolled plate is small, a large amount of coarse precipitates are generated, and the magnetism deteriorates. Further, D5 and D6 cannot secure a time of 1100 ° C. or higher at the stage of slab heating, and the magnetism deteriorates due to improper precipitation of precipitates or generation of a large amount of coarse precipitates. You can check. Since the hot-rolled plate annealing time of D7 and D8 is excessively long or excessively short, it can be confirmed that the precipitates are generated in an excessively small amount or in an excessively large amount, and the magnetism is deteriorated.

Experimental Example 5
By weight% Si: 2.8%, Al: 0.029%, S: 0.001%, Mn: 0.15%, N: 0.003%, C: 0.025%, Ti: 0.002 %, P: 0.05%, and a slab composed of the balance Fe and unavoidable impurities was produced. The slab was heated at 1150 ° C. and then hot-rolled to produce a hot-rolled coil having a thickness of 1.6 mm. After the slab was manufactured, the hot rolling end times were arranged in Table 9 below. Table 9 summarizes the maximum temperature from the stage of heating the slab to the stage of manufacturing the hot-rolled plate. At the time of hot rolling, the reduction rate of the final pass and the reduction rate of the pass before the final pass are arranged in Table 9, and the total reduction rate of the final pass and the previous pass is arranged in Table 9 below. The hot-rolled annealed sheet, which was annealed at 1100 ° C. to 1140 ° C. for 30 seconds, annealed at 900 ° C. for 90 seconds, and then rapidly cooled, was cold-rolled to a reduction rate of 63%.

The cold-rolled plate was subjected to a primary recrystallization annealing step of nitriding to 0.02 wt% and decarburizing at a dew point of 60 ° C. and a hydrogen of 75% atmosphere so that the crystal grain size was as shown in Table 7 below. Then, after applying an annealing separator containing an MgO component, the temperature was raised to 1200 ° C. at a heating rate of 20 ° C. per hour, and then secondary recrystallization annealing was carried out over 20 hours. Insulation coating was applied, magnetism was measured, and Table 10 was arranged.

As shown in Tables 9 and 10, it can be confirmed that the invention examples satisfying all the conditions are excellent in magnetism. On the other hand, it can be confirmed that E3 has inferior magnetism because the rolling reduction of the final pass and the pass before the final pass in hot rolling is high. Since the total reduction rate of the final pass and the pass before the final pass in hot rolling is high in E4, it can be confirmed that the magnetism is inferior. Since it takes a long time from the production of the slab to the hot rolling of E5, it can be confirmed that the magnetism is inferior. In E6, the maximum temperature of hot rolling after slab production is higher than the hot-rolled sheet annealing temperature, and the final pass reduction rate is low, so it can be confirmed that the magnetism is inferior.

The present invention is not limited to the above-mentioned examples, and can be produced in various forms different from each other, and a person having ordinary knowledge in the technical field to which the present invention belongs is required to have the technical idea of the present invention. It should be understood that it can be implemented in other concrete forms without changing the characteristics of. Therefore, it should be understood that the examples described above are exemplary in all respects and are not limiting.

Claims (24)

By weight%, Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0.003%, Mn: 0.02 to 1.0%, N: 0.003% or less (excluding 0%), C: 0.01% or less (excluding 0%), Ti: 0.01% or less (excluding 0%), P: 0.005 to 0.10. A bidirectional electromagnetic steel sheet containing%, the balance being Fe and other unavoidable impurities, and satisfying the following equation (1).
[Number 1]
[Mn] / [S] ≧ 60
(In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S, respectively.) The bidirectional electromagnetic steel plate according to claim 1, further comprising one or more of Sb: 0.001 to 0.1% by weight and Sn: 0.001 to 0.1% by weight. Mo: 0.01% by weight or less, Bi: 0.01% by weight or less, Pb: 0.01% by weight or less, Mg: 0.01% by weight or less, As: 0.01% by weight or less, Be: 0.01 The bidirectional electromagnetic steel plate according to claim 1, further comprising one or more of Sr: 0.01% by weight or less. The bidirectional electromagnetic steel sheet according to claim 1, wherein the surface integral of the crystal grains having an orientation within 15 ° from {100} <001> is 60 to 99%. Claim 1 is characterized in that a forsterite layer is formed on the electromagnetic steel sheet, and the forsterite layer has a fraction of an area having a thickness within 2 μm from the surface of the electromagnetic steel sheet of 75% or more. Bidirectional electromagnetic steel sheet described in. An insulating layer is formed on the forsterite layer, and the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer are 0.2 to 8 μm, respectively.
The bidirectional electromagnetic steel sheet according to claim 5, wherein the difference between the thickness of the upper surface insulating layer and the thickness of the lower surface insulating layer is 50% or less of the thickness of the lower surface insulating layer. The average roughness (Ra) of the upper surface insulating layer and the average roughness (Ra) of the lower surface insulating layer are 1 μm or less, respectively.
The bidirectional electromagnetic steel sheet according to claim 6, wherein the difference between the average roughness (Ra) of the upper surface insulating layer and the average roughness (Ra) of the lower surface insulating layer is 0.3 μm or less. The first aspect of claim 1, wherein Br in the rolling direction and Br in the rolling vertical direction are all 1.65 T or more, Br in the circumferential direction is 1.55 T or more, and Br is calculated by the following equation 2. Bidirectional electromagnetic steel plate.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the Si and Al contents (% by weight), respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. .) The two directions according to claim 1, wherein the magnetic permeability UDC at a measurement frequency of 0.01 Hz or less is 1.2 times or more the magnetic permeability U50 at 50 Hz when a magnetic field of 1.5 T is applied. Electrical steel sheet. The first aspect of the present invention is that the Br value measured after annealing the electromagnetic steel sheet at a temperature of 750 ° C. to 880 ° C. for 1 to 2 hours is 1.65 T or more, and Br is calculated by the following equation 2. The described bidirectional electrical steel sheet.
[Number 2]
Br = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B8
(In Equation 2, [Si] and [Al] indicate the Si and Al contents (% by weight), respectively. B8 indicates the strength of the magnetic field (Tesla) induced when induced at 800 A / m. .) The Bh in the rolling direction is 1.8T or more, the Bh in the vertical rolling direction is 1.7T or more, the Bh in the circumferential direction is 1.6T or more, and the Bh is calculated by the following equation 3. The bidirectional electromagnetic steel sheet according to claim 1.
[Number 3]
Bh = 7.87 / (7.87-0.0.065 × [Si] -0.1105 × [Al]) × B25
(In Equation 3, [Si] and [Al] indicate the Si and Al contents (% by weight), respectively. B25 indicates the strength of the magnetic field (Tesla) induced when induced at 2500 A / m. .) By weight%, Si: 2.0 to 6.0%, Al: 0.0005 to 0.04%, S: 0.0001 to 0.003%, Mn: 0.02 to 1.0%, N: 0.001 to 0.01%, C: 0.02 to 0.06%, Ti: 0.01% or less (excluding 0%), P: 0.005 to 0.10%, the balance is The stage of producing a slab consisting of Fe and other unavoidable impurities and satisfying the following number 1.
The stage of heating the slab,
The stage of hot-rolling the slab to produce a hot-rolled plate,
The stage of cold-rolling the hot-rolled plate to manufacture a cold-rolled plate,
A method for producing a grain-oriented electrical steel sheet, which comprises a step of primary recrystallization annealing of the cold-rolled plate and a step of secondary recrystallization annealing of the primary recrystallization-annealed cold-rolled plate.
[Number 1]
[Mn] / [S] ≧ 60
(In Equation 1, [Mn] and [S] indicate the contents (% by weight) of Mn and S in the slab, respectively.) The method for manufacturing a grain-oriented electrical steel sheet according to claim 12, wherein the slab satisfies the following equation (4).
[Number 4]
[C] / [Si] ≧ 0.0067
(In Equation 4, [C] and [Si] indicate the contents (% by weight) of C and Si in the slab, respectively.) The method for manufacturing a grain-oriented electrical steel sheet according to claim 12, wherein the reduction ratio is 50 to 70% at the stage of manufacturing the cold-rolled plate. The method for producing a grain-oriented electrical steel sheet according to claim 14, wherein the amount of nitriding is 0.01 to 0.023% by weight at the stage of primary recrystallization annealing. The method for producing a bidirectional electromagnetic steel sheet according to claim 15, wherein after the step of primary recrystallization annealing, the average crystal grain size of the primary recrystallized annealed steel sheet is 32 to 50 μm. After the step of manufacturing the hot-rolled plate, the temperature of the step of annealing the hot-rolled plate (T2) and the temperature of the stage of heating the slab (T1) are further included in the step of annealing the hot-rolled plate. The method for manufacturing a bidirectional electromagnetic steel plate according to claim 12, wherein the bidirectional electromagnetic steel plate is satisfied.
[Number 5]
-200 ≤ T1-T2 ≤ 30 The method for producing a grain-oriented electrical steel sheet according to claim 17, wherein the time of 1100 ° C. or higher is 25 to 50 minutes at the stage of heating the slab. The method for producing a grain-oriented electrical steel sheet according to claim 18, wherein the time at 1100 ° C. or higher is 5 to 50 seconds at the stage of annealing the hot-rolled sheet. The method for producing a grain-oriented electrical steel sheet according to claim 19, wherein after the step of annealing the hot-rolled plate, the average crystal grain size of the hot-rolled plate is 100 to 200 μm. After the step of annealing the hot-rolled plate, the number of precipitates having a particle size of 0.1 μm or more in a ^{1 mm 2 area of the hot-rolled plate is 100 to 4000.}
The feature is that the ratio (A / B) of the number of precipitates (A) having a particle size of 0.1 to 0.5 μm to the number of precipitates (B) having a particle size exceeding 0.5 μm is 1 or more. The method for manufacturing a bidirectional electromagnetic steel plate according to claim 20. After the step of manufacturing the hot-rolled plate, the step of annealing the hot-rolled plate is further included.
The time from the step of heating the slab to the step of manufacturing the hot-rolled plate is 3 to 20 minutes, and the maximum temperature from the step of heating the slab to the stage of manufacturing the hot-rolled plate is the hot-rolling. The method for producing a bidirectional electromagnetic steel plate according to claim 12, wherein the annealing temperature at the stage of annealing the plate is 20 ° C. or lower. At the stage of manufacturing the hot-rolled sheet, two or more passes are included, the reduction rate in the final pass and the pass before the final pass is 15 to 40%, respectively, and the reduction in the final pass and the pass before the final pass, respectively. The method for manufacturing a grain-oriented electrical steel sheet according to claim 21, wherein the total rate is 55% or less. The method for producing a grain-oriented electrical steel sheet according to claim 12, further comprising a step of applying an annealing separator containing MgO after the step of primary recrystallization annealing.